Patent GB-666309-A (GB)
Title: Improvements in hydraulic pumps and motors
IPC: F01B3/00
Filed: 1948-12-20
Abstract: 666,309. Hydraulic transmission of power; liquidpressure engines. MITCHELL, W. Sept. 21, 1949 [Dec. 20, 1948], No. 32849/48. Class 69 (ii) [Also in Group XXVIII] In a variable-delivery pump or a hydraulic motor comprising a cylinder block 1 with a shaft 4 mounted therein so as to permit relative rotational movement between the shaft 4 and the block 1, the latter including at least one cylinder 29 disposed parallel to the axis of the shaft 4, the cylinder' housing a pair of axially-aligned oppositely-acting pistons 38, 39, the outer ends of each of which bear directly or through thrust-transmitting means, suCh as balls 41, against one of two spaced swash plates 10, 14 arranged on the shaft 4 so that their working faces are each at a fixed inclination to the shaft axis and conform with the shaft in its relative rotational movement thereby to impart reciprocating movement to the pistons in the case of a pump, or to convert reciprocating movement of the pistons into a rotation of the swash plates in the case of a motor, it is arranged that at least one of the swash plates is angularly adjustable on the shaft; the swash plates may also be arranged with their working faces inclined to the driving axis and capable of assuming different relative inclinations with respect to each other for varying the effective timing of the various piston strokes. The left-hand swash plate 10 is' secured to the shaft 4, which is journalled in the cylinder block 1 that is arranged as two coaxial parts separated by a partition 2, whilst at the other end the shaft 4 is splined to receive a sleeve 12 that is externally threaded to accommodate the right-hand swash plate 14 which its therefore angularly but not axially adjustable in relation to . the other swash plate 10, depending upon the extent the sleeve 12 is pushed along the shaft 4 by twin racks 24 operable from a hand wheel 19 through a twin worm and wheel gear 20 and 21. The cylinders 29 in block 1 are provided with liners 30 which are rotated in the block 1 by gearing 31 and 32 from the shaft 4, alternate liners being rotated from opposite ends of the shaft. Each liner 30, which is provided with an inlet port 36 and outlet port 37, acts as a valve to connect each cylinder to a common annular inlet or exhaust port 33, 34, respectively, one being machined in each opposing face of the two parts of the block; each annular port 33, 34 communicates with a manifold, not shown. Opposed pistons 38, 39 mounted within each liner are axially bored to accommodate compression springs 40 so that balls 41 in the outer piston ends are maintained against the swash plates 10 and 14. The timing for each liner 30 is so arranged as to connect inlet port 36 with port 33 during outward movement of the pistons and outlet port 37 with port 34 during inward piston movement, at which time the swash plates have a maximum opposite inclination, as shown. When operated as a motor both swash plates may be fixed. Swash plates with two or more working faces may be used if it is desired to impart two or more working strokes to each piston for each revolution of shaft 4. A pump and a motor may be arranged to form a hydraulic transmission. When used as a pump a separate inlet and delivery port is provided for each cylinder in place of ports 33 and 34. In a modification, the left-hand swash plate may be made adjustable either separately or by the same mechanism as that used to adjust the right-hand swash plate.